Preheat oven to 350oF (180oC).Line baking Tray (7.3 x 5.4 x 2.0 inch;18.5 x 13.6 x 5.1 cm) with parchment paper. Set aside. To a bowl, add sugar and water. Whisk until sugar is completely dissolved.
Then add cocoa powder, peanut butter and sweet potato. Mix.
Transfer batter to baking tray. Spread evenly. Top with chocolate chips.
Bake in preheated oven to 350oF (180oC), rack middle position, 20 minutes for fudgy texture or 25 minutes for cake texture.